Telephone transmission system



July 15 1924. 1,501,693

R. S. WILBUR TELEPl-iOIEA TRANSMISSION SYSTEM Filed Nov. 25 1919 y @inPatented July 15, 1924.

UNITED STATES PATENT carica.

RAY S. WILBUR, DE LYND'HURST, NEW JERSEY, ASSIG-NOR TO- WESTERN ELECTEICCOMPANY, INCORPORATED, OF NEW YORK, N. Y., A CORPORATION O F NEWTELEPHONE TRANSMISSION SYSTEM.

Application fried November 25, 191e. serial No. 340,480.

To allzu/wm t may conce/1h71:

Be it lfznown that I, RAY S. l/TILBUR, a citizen of the United States,residing at Ljfndhurst, in the county of Bergen, State of ew Jersey,have invented certain new and useful Improvements in TelephoneTransmission Systems, of which the following is a full, clear, concise,and exact description. Y'

i This invention relates to improvements in telephonesystems, and hasparticular reference toy the four-'wire repeater circuit therefor.

In transmission lines, it is common to pro- Y vide amplifying means forreinforcing currents of low frequency, such as employed insignalingbetween operators or subscribers. It is also desirable toimpress upon a metallic circuit, simultaneously with the transmission ofringing current, other signaling current such as employed for the Morsecode.

'It has been customary, in four-wire repeater circuits, whentransmitting ringing current, for instance, from a terminating` circuitover an outgoing line, to operate an electromagnetic device for theurpose of supplying ringing current to sait line. rThe operation of thisdevice opens and unbalances the outgoing line while ringing current isbeing applied and thereby prevents the transmission of metallic Morsesignaling current.

An object of this invention is to prevent unbalancing of the outgoingcircuit when applying ringing current thereto, whereby other signalingcurrent may be impressed upon the line or metallic side of said'fcircuitsimultaneously with said ringing current.

The drawing illustrates diagrammatically a four-wire repeater circuitshowing the application of the invention thereto.

' 1n the drawing, A designates an incoming line, B a terminating circuitand C an outgoing line. Ringing current transmitted over the incomingline A is induced into the secondary winding of the repeating coil l,from thence to the back' cont-acts and up per and middle armatures ofrelay 2, the back contacts and armatures of relay 8, and

then to 'the'primary' winding of the repeating coil Il; A low frequencyfilter consisting of condensers 5 and a bridged induct-ance 6 isemployed to lter out ringing and voice currents below a certain range offrequency -so that all ringing current will be diverted to the primarywinding of the repeating coil el., as before stated. This ringingcurrent-is respond to this amplified current is ener` gized. This causesthe energization of relay 9 which is made slow to release so that thesame will remain energized during any momentary deenergization of relay'SYdu'e'j toia decrease in the amplification ofthe current passingthrough the Winding thereof.` Energization of relay 9 connects a sourceof ring'- ing current 10, preferably of 1623- cycle frequency, to theterminating circuit B, through the middle and lower armatures and frontconta cts of relay 9, resistances Ofanto-transformer 11 and primaryvwindings ofwth'e three-winding transformer 12.` The attraction of theupper armature of relay9 closes a bridge Vacross the lineAfthrough're'sistance 13 and thus prevents unbalancingof the line. Voicecurrentswithin "the usual range of frequency willvpass from one line toanother through the' normal contacts `of relays 2, 3 and 9 after thelatter relay has released its armatures at the termination'of theapplication of ringingcurrent to the circuit B.

Ringing current of the usual 16% cycle frequency transmitted from theterminating circuit B passes to the middle lpoi-nts of the three-windingtransformer 12, the autotransformer '11, normal `contacts of the middleand lower armatures of relay 9 and the windings of the ringing responserelay 14. This relay is responsive to the ringing current and, by itsenergization, opensfthe energizing circuit of relay 15 whichreleases'its armature. A circuit is then closed from grounded battery,through the windings of relays 2 and 3 in parallel, and the armature andcontact of relay 15, to ground. Relays 2 and 3 are energized. Relay 2,by attracting its armatures, disconnects the incoming line A and bridgessaid line through resistance 16, to prevent unbalancing of the lineduring the application 'of ringingcurrent. Relays 2 and 3 connectVringing current, preferably of a frequency of 133 cycles, from a source17 through alternate contacts of said relays, and from'th'ence to thekWindings of a transformer 18 which'is connected The current is hereamplified in the usual manner and a relay 8 tuned* to` transn'iittedfrom. the secondary windings of the three-winding transformer, overthesides of the outgoing line C, through the re 3eatmg coil 19. inasmuch asline C is not opened during the transmission of ringing currentthereover, as is apparent from the foregoing, the line Awill remainbalanced or continuous to permit of the application of other signalingcurrent thereto, wnile said ringing current is being applied. Voicecurrents will be transmitted from circuit B directly through the primaryand secondary windings of three-winding transforme-r l2 to the line C.

The advantage of the feature just mentioned, of not opening line Cduring the transmission of ringing current thereover will be apparent ifwe consider that line C inha'ddition to beingemployed for transmittingspeech currents is also employed for two-wayY metallic telegraphoperation. The usual method of duplexing a two-wire line for telegraphsignals is to shunt the line by a suitable bridge 30, connectionstherefrom being talen to the usual telegraph relay and balancing'network. This balancing network is, of course, adapted to match theimpedance of the line as seen from leads 32 and which would be thecombined iinpedance of outgoing line C and the impedance looking in thedirection of line B whereby the local receiving` equipment will not beactuated by the outgoing telegraph signals. lt would, therefore, followthat if in applying the ringing currents from generator 17 to outgoingline C, the line were temporarily opened, the impedance of the systemconnected to leads 352 and would be changed, thereby unbalancing thetelegraph equipment and preventing the successful. duplex operationthereof.

TFilliat is claimed is:

l, in a telephone system, a two-wire circuit., a four-wire circuit, athree-limb transformer for coupling one side of said fourwire circuit tosaid two-wire circuit, a source of ringing currents, and meansresponsive to ringing currents in said twowire circ-uit for impressingcurrents from said source upon said side of said fourivire circuitiviiile maintaining fixed thereonnections of said side to saidtransformer.

2. ln combination, a local station comprisingterminals of a terminatingcircuit, terminals of an outgoing line, an artificial balancing line forsaid circuit, a three-wind- ;ing transformer having a winding in saidcircuit, a winding in said balancing line and a. third winding in saidoutgoing line, a local4 generator of ringing currents, and meansresponsive to ringing currents from a distant station for impressingringing currents from said generator upon the mid points of the firsttwo windings of said transformer to transmit said currents to saidterminating circuit.

.9i signaling station, a plurality of lines terminating at said station,a network for balancing one of said lines, a three winding transformerhaving a. winding in circuit 1with said first line, a second winding incircuit with said balancing network and a third winding in circuit witha second line, a third line being connected to the mid- A points of saidfirst two windings, a local generator of ringing currents, and meansresponsive to ringing currents in said third line for impressing ringingcurrents upon the midpoints of said first two windings.

el. ln combination, a signaling station, a foiuf-wire circuit and atwo-wire circuit terminating at said station, said station comprisingmeans for coupling said circuits, a source of ringing currents, andmeans responsive to ringing currents in said twowire circuit fordisconnecting one side of said founwire circuit from said coupling meansand for impressing ringing currents from said source upon the other sideof said four-wire circuit.

)i telephone signaling station, fourwire circuit and a two-wire circuitterminating at said station, means for coupling s id circuits, means inone side of said fourwire circuit for prevent-ing ringing currents fromthe said one side of said four-wire circuit from being impresseddirectly upon said two-wire circuit, a plurality of sources of ringing`current, means comprising movable contacts in the said one side of saidfour-wire circuit and responsive to ringing currents in said two-wirecircuit for connecting one or" said sources to the other side of saidfour-wire circuit, and means com.- prising movable contacts in the saidone side of said four-wire circuit and responsive to ringing currents insaid four-wire circuit for connecting another of said sources to saidtwo-wire circuit.

6. A telephone signaling station, a twowire circuit and a four-wirecircuit terminating in said station, said station compris ing means forcoupling said circuits, a plurality of movable contacts included in thespeech transmission path of one side of said four-wire circuit, meansresponsive to ringing current originating in said two-wire circuit foroperating certain of said contacts, and means responsive to ringingcurrent. originating in one side of said fourwire circuit for operatingother of said contacts.

7. ln combination, a three-winding transformer, a line in circuit withone winding lll() llO.

of said transformer, a balancing network.

for said line in circuit with a second Windlll ing of said transformer,a second line in circuit with the third winding of said transformer. asecond transformer having a winding in circuit with said second line, asource of signaling currents, and means responsive to signaling currentsin said first line for connecting said source to said sccondtransformer.

8. signaling station. a four-wire circuit and a two-wire circuitterminating at. said station. connections coupling both sides of saidfour-wire circuit to said two-wire circuit, said connections beingtraversed by ringingcurrents from said two-wire circuit, a local sourceof ringing currents, and means responsive to ringing currents in saidtwo-wire circuit for impressing ringing currents from said source uponone side of said four-wire circuit while maintaining fixed theconnections of the said one side to said two-wire circuit.

9. In combination, a three-winding transformer, a line connected incircuit with one winding of said transformer, a balancing network forsaid line in circuit with the second winding of said transformer, asecond line in circuit with the third winding of said transformer, athird line connected to the midpoints of said first two windings, alocal source of signaling currents, and means responsive. to signalingcurrents originating in said first line for impressing currents fromsaid source upon one of said other lines while maintaining fixed theconnection of said last-mentioned line to said transformer.

10. In combination, a line for the transmission of signals of one typein either direction. a second line for the transmission of signals ofone type in onedirection only, a signaling station comprising means forcoupling said lines, movable contacts in said second line, meanscontrolled by currents in said first line for controlling certain ofsaid contacts. and means controlled by currents in said second line forVcontrolling other of said contacts.

11. In combination, a line for the transmission of signals of one typein either direction. a second line for the transmission of signals ofone type in one direction only, a signaling station comprising couplingmeans for said lines, and means comprising movable members responsive tosignaling currents from said first line for impressing signalingcurrents upon said second line while maintaining fixed the connectionsof said second line to said coupling means.

12. In combination, a line for the transmission of signals of one typein either direction, a second line for the transmission of signals ofone type in one direction only, a signaling station comprising means forcoupling said lines, a local source of ringing currents. and meansresponsive to ringing currents in said first line for impressing ringingcurrents from said source upon said second line whiie maintaining fixedthe connections of said second line to said coupling means.

13. In combination, a two-wire line, a four-wire line, means forcoupling said lines, a source of signaling currents, a local networkhaving an impedance approXimating the impedance of one side of saidfourwire lines, and means responsive to signaling currents in saidtwo-wire line for applying signaling currents from said source to oneside of said four-wire line, for breaking` the connections between saidcoupling means and the other side of said four-wire line. and forconnecting to said network that part of said b-roken side away from saidcoupling means.

14. In combination, a two-wire line, a four-wire line, coupling meansfor said. lines, a source of signaling currents, a local network havingan impedance approximating the impedance of one side of said fourwireline, and means responsive to signaling currents in one side of saidfour-wire line for applying signaling currents from said source to saidtwo-wire line, for breaking the connections between said coupling meansand the said one side of said fourwire line, and for connecting saidnetwork to the part of said broken side located away from said couplingmeans.

15. In a telephone system. a two-wire circuit, a four-wire circuit,means coupling one side of said four-wire circuit to said two-wirecircuit, a source of ringing currents, and means responsive to ringingcurrents in said two-wire circuit for impressing currents from saidsource upon said side of said four-wire circuit while maintaining fiXedthe connections of said side to said two-wire circuit.

In witness whereof, I hereunto subscribe my name this 21st day ofNovember A. D.

RAY S. IVILBUR.

